Description of Prior Arts
A basic method for producing the grain-oriented magnetic steel sheet was disclosed by N. P. Goss in U.S. Pat. No. 1,965,559, and since then the grain-oriented magnetic steel sheets have been commercially produced thereby in a large amount. After the discovery of the basic method by N. P. Goss, the good magnetic properties of the grain-oriented magnetic steel sheets have been found by other researchers to be attributable to the fact that the grain orientation in these materials are in-comparably higher than that obtained by other magnetic materials known at that time.
In the grain-oriented magnetic steel sheets, the rolling direction coincides with the easily magnetizable crystal axes, namely &lt;001&gt; as defined by means of the Miller Crystallo-graphic Index System, and the steel sheet surface is composed of the grains having an orientation of {110}&lt;001&gt; which is parallel to the {110} plane, also as defined by means of the Miller Index.
Inventors and discoverers in the field of the grain orientation of grain-oriented magnetic steel sheets after the discovery of N. P. Goss were all, excepting a few, concerned with how to make the grain orientation follow the Goss's ideal grain orientation of {110}&lt;001&gt; for improvements of the magnetic flux density in the rolling direction, hence reduction of the core losses.
In particular, Taguchi et al disclosed in U.S. Pat. No. 3,287,183, a method which can produce, by a simplified process, a grain-oriented magnetic steel sheet having such a very high integration that the average displacement angle of individual grains from the ideal grain orientation of {100}&lt;001&gt; falls within a range of 3.degree., thus having a very high magnetic flux density in the rolling direction, and this method by Taguchi et al has been widely used on a larger commercial scale and has been replacing the Goss method.
Thus, to summarize, for the past ten years since the invention of the grain-oriented magnetic steel sheet by N. P. Goss, it has been generally considered to be best means for the improvement of the magnetic properties to approach the Goss's ideal orientation of {110}&lt;001&gt; as shown in FIG. 1.